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Limiter.cpp
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Limiter.cpp
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#include "limiter.h"
namespace {
template <typename T> T clip(T x, T low, T high)
{
return std::max(low, std::min(high, x));
}
}
void SoftClipper::process(const float *in, size_t nin, float *out, size_t *nout)
{
for (int n = 0; n < m_nchannels; ++n) {
std::vector<float> &x = m_buffer[n];
x.reserve(x.size() + nin);
for (size_t i = 0; i < nin; ++i)
x.push_back(clip(in[i * m_nchannels + n],
-3.0f * m_thresh, 3.0f * m_thresh));
ssize_t limit = x.size();
if (limit > 0 && nin > 0) {
float last = x[limit-1];
for (; limit > 0 && x[limit-1] * last > 0; --limit)
;
}
ssize_t end = m_processed[n];
while (end < limit) {
ssize_t peak_pos = end;
for (; peak_pos < limit; ++peak_pos)
if (x[peak_pos] > m_thresh || x[peak_pos] < -m_thresh)
break;
if (peak_pos == limit)
break;
ssize_t start = peak_pos;
float peak = std::abs(x[peak_pos]);
while (start > end && x[peak_pos] * x[start] >= 0)
--start;
++start;
for (end = peak_pos + 1; end < limit; ++end) {
if (x[peak_pos] * x[end] < 0)
break;
float y = std::abs(x[end]);
if (y > peak) {
peak = y;
peak_pos = end;
}
}
if (peak < m_thresh * 2.0) {
float a = (peak - m_thresh) / (peak * peak);
if (x[peak_pos] > 0) a = - a;
for (ssize_t i = start; i < end; ++i)
x[i] = x[i] + a * x[i] * x[i];
} else {
float u = peak, v = m_thresh;
float a = (u - 2 * v) / (u * u * u);
float b = (3 * v - 2 * u) / (u * u);
if (x[peak_pos] < 0)
b *= -1.0;
for (ssize_t i = start; i < end; ++i)
x[i] = x[i] + b * x[i] * x[i] + a * x[i] * x[i] * x[i];
}
}
m_processed[n] = limit;
}
size_t prod = std::min(*nout, *std::min_element(m_processed.begin(),
m_processed.end()));
size_t k = 0;
for (size_t i = 0; i < prod; ++i)
for (int n = 0; n < m_nchannels; ++n)
out[k++] = m_buffer[n][i];
for (int n = 0; n < m_nchannels; ++n) {
std::vector<float> &x = m_buffer[n];
if (x.size() && prod) {
std::rotate(x.begin(), x.begin() + prod, x.end());
x.resize(x.size() - prod);
m_processed[n] -= prod;
}
}
*nout = prod;
}